Process for the manufacture of synthetic bulky filament fibers

ABSTRACT

A PROCESS FOR CRIMPING SYNTHETIC THERMOPLASTIC CONTINUOUS FILAMENT YARNS IS DISCLOOSED WHICH COMPRISES FORCIBLY PASSING A PLURALITY OF CONTINUOUS FILAMENT YARNS AGAINST PRESSURE, INTO A STUFFING BOX THROUGH A PAIR OF NIP ROLLS, AT LEAST ONE OF WHICH IS HEATED, WHEREIN THE FILAMENTS ARE FED TO THE NIP ROLLS IN A MANNER SUCH THAT THE FILAMENTS ARE ARRANGED INTO FROM 2 TO 3 COMPACTED LAYERS AT THE POSITION WHERE THE FILAMENTS ENTER THE NIP LINE FORMED BY THE NIP ROLLS BY LATERALLY CONFINING THE FILAMENTS AT THE NIP LINES, THEREBY ASSURING THAT EACH FILAMENT TIGHTLY CONTACTS EACH ADJACENT FILAMENT AND THAT THE FILAMENTS SUBSTANTIANTIALLY FILL THE SPACE AT THE NIP LINE FORMED BETWEEN THE NIP ROLLS, SUCH A PROCESS RESULTS IN LOOPED CRIMPS IN THE FILAMENT YARNS IN A DIRECTION SUBSTANTIALLY PERPENDICULAR TO   THE PLANE OF THE NIP LINE, THE LOOPED CRIMPS ARE FORMED IN A PARALLEL FASHION IN THE CONTINUOUS YARNS FED THROUGH THE STUFFING BOX, THE WORD &#34;PARALLEL&#34; INDICATING THAT THE INDIVIDUAL FILAMENTS ARE CRIMPED IN UNISON IN ORDER TO MORE EASILY SEPARATE THE INDIVIDUAL FILAMENTS OR GROUPS OF FILAMENTS FROM THE PLURALITY OF YARNS FED THROUGH THE NIP ROLLS AND THROUGH THE STUFFING BOX.

June 11, 1974 HIROSHI KASHIMA ETAL PROCESS FOR THE MANUFACTURE OF SYNTHETIC BULKY FILAMENT' FIBERS 3 Sheets-Sheet 1 Filed March 15, 1972 FlG. B

L A N m T N E V N O C June 11, 1974 HiROSHl KASHIMA ET AL PROCESS FOR THE MANUFACTURE 01-" SYNTHETIC BULKY FILAMENT FIBERS 3 Sheets-Sheet Filed March 15, 1972 FIG June 11, 1974 HIROSHI KASHIMA ETAL 3,816,583

PROCESS FOR THE MANUIACI'URE OF SYNTHETIC BULK! FILAMENT FIBERS Filed March 15, 1972 3 Sheets-Sheet :5

CONVENTIONAL FIG. 6

FIG. 9

United States Patent 3,816,583 PROCESS FOR THE MANUFACTURE OF SYNTHETIC BULKY FILAMEN T FIBERS Hiroshi Kashima, Hideyuki Tsujimoto, and Toshiaki Kakuda, Osaka, Japan, assiguors to Asahi Kasei Kabushiki Kaisha, Osaka, Japan Continution-in-part of application Ser. No. 37,471, May 18, B70, which is a continuation of application Ser. No. 694,466, Dec. 29, 1967, both now abandoned. This application Mar. 15, 1972, Ser. No. 234,872 Claims priority, application Japan, Dec. 30, 1966, 42/85,905 Int. Cl. B29c 15/00 US. Cl. 264-282 11 Claims ABSTRACT OF THE DISCLOSURE A process for crimping synthetic thermoplastic continuous filament yarns is disclosed which comprises forcibly passing a plurality of continuous filament yarns against pressure, into a stufiing box through a pair of nip rolls, at least one of which is heated, wherein the filaments are fed to the nip rolls in a manner such that the filaments are arranged into from. 2 to 3 compacted layers at the position where the filaments enter the nip line formed by the nip rolls by laterally confining the filaments at the nip lines, thereby assuring that each filament tightly contacts each adjacent filament and that the filaments substantially fill the space at the nip line formed between the nip rolls. Such a process results in looped crimps in the filament yarns in a direction substantially perpendicular to the plane of the nip line. The looped crimps are formed in a parallel fashion in the continuous yarns fed through the stufling box, the word parallel indicating that the individual filaments are crimped in unison in order to more easily separate the individual filaments or groups of filaments from the plurality of yarns fed through the nip rolls and through the stuffing box.

CROSS-REFERENCE TO RELATED APPLICATIONS The present application is a continuation-in-part of Ser. No. 37,471, filed May 18 1970, which is, in turn, a continuation of Ser. No. 694,466, filed Dec. 29 1967, both now abandoned.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a process for the manufacture of crimped synthetic thermoplastic fiber filaments relying upon the conventional stutter box crimping technique.

Description of the prior art Various and profound efforts have been directed to the manufacture of synthetic bulky yarns. For this purpose, th stutter box crimping technique has recently been developed and improved. According to a representative method synthetic fiber filaments are forcibly and continu ously fed through a pair of nip rolls located at the inlet opening of a stuffer box, and stulfed into a pressurized ice mass, so as to provide fine and delicate crimps to the filaments, while, at the same time, the processed and heat-set filaments are being taken out continuously from the pressurized outlet opening of the stutter box. For this purpose, the outlet opening is a pressurized and pivotable cover plate and the crimped filaments are delivered forcibly through the limited outlet opening formed between the stufier box proper and the pivotable end plate which is loaded with an adjustable closing force by means of, for example, a loading spring or weight, as the case may be.

In the thus processed continuous filaments, primary and secondary crimps are observed. Although the precise mechanism of the generation of these crimps has not yet been determined it may be definitely observed that the thus-generated primary crimps form a zigzag or sawtoothlike shape comprising straight line portions connected one after another by slightly rounded apexes.

In the conventional crimping technique as disclosed in U.S. Pats. 2,575,837 and 2,575,838, for instance, the crimps are generated substantially in the parallel direction to the nip line formed by the pair of feed or nip rolls. It is, however, highly diflicult to divide the large number of such processed or crimped filaments into bundles adapted for the preparation of yarns, threads or the like due to the complicated and thus difiicult-to-separate tangles of crimps formed on the filaments. Formation of such tangles of crimps, if developed, will considerably reduce the operational efliciency in the manufacture of yarns made of crimped synthetic filaments.

Through investigations of the crimps developed according to conventional stuifer box techniques it has been discovered that there are two kinds of crimps. Predominant crimps are directed in the axial direction when seen in the longitudinal direction of the nip rolls (i.e., in a direction parallel to the nip line). These crimps are of saw-tooth configuration. A small percentage of the crimps, however, are directed in the perpendicular direction relative to the aforementioned nip line. It has been surprisingly observed that these vertical crimps, relative to the nip line, are in the form of a loop configuration which has a considerable similarity to those of natural animal fiber crimps, thus being highly dilferent from artificial crimps generated according to the known technique.

Accordingly, it is a primary object of the present invention to provide a stutter box crimping process capable of providing vertical looped crimps in synthetic thermoplastic continuous filament yarns which crimps are substantially difierent from conventionally-produced artifical crimps and substantially similar to the crimps formed naturally in natural fibers such as wool and the like.

It is a further object of the present invention to provide an improved filament crimping process capable of generating primary (i.e., predominantly) crimps formed in parallel planes perpendicular to the nip lines formed between the nip rolls.

It is a further object of the present invention to provide an improved crimping process for synthetic thermoplastic continuous filament yarns wherein parallel looped crimps are formed in said yarns in order to allow the individual filaments or groups of filaments to be easily separated from one another after crimping.

Other objects and advantages will become apparent from the ensuing description.

SUMMARY OF THE INVENTION The present invention mainly provides a process for the generation of looped crimps in continuous filament yarns which are, in addition, oriented in parallel planes perpendicular to the nip line, to thereby provide for easy filament separation to be carried out at a further processing stage, preferably following the crimping stage, in order to divide the crimped filaments into bundles as a preparatory step for the manufacture of yarns and the like.

It has been found that in order to fulfill the aforementioned objects, the manner in which the filaments are fed to the nip line formed between the nip rolls is of critical importance.

According to the present invention, the filaments are forcibly controlled in their feeding position at the nip line so as to generate predominantly vertical crimps, thus preventing otherwise possible lateral crimps. The term vertical used herein throughout the present specification indicates that direction which is perpendicular to the nip line in the aforementioned sense. On the contrary, the term lateral as used herein indicates that direction parallel to the nip line.

Accordingly, the present invention provides a process for producing looped parallel crimps in a vertical direction relative to the nip line in continuous filament thermoplastic yarns which comprises feeding a plurality of filament yarns through a pair of nip rolls, at least one of which is heated to a specified temperature depending upon the material constituting said yarns, into a stulfing box wherein the filaments are forcibly arranged into form 2 to 3 compacted layers at the position where the filaments enter the nip line formed by the nip rolls, it being necessary that each filament tightly contacts each adjacent filament at the nip line such that the filaments substantially fill the space at the nipline. Depending upon the length of the nip line formed by the nip rolls at the entrance to the stufiing box, the number of filaments to be fed thereto can be easily selected to assure that from 2 to 3 compacted layers of filaments are provided at the nip line. In addition, depending upon the particular material constituting the filaments, the temperature of the at least one nip roll which is heated, as well as the temperature to which the filaments are pre-heated prior to being fed to the nip line, if desired, can be adjusted to provide optimum crimping capabilities in the continuous filament thermoplsatic yarns.

An additional, yet remarkable advantage of the present invention is that the aforementioned requirements can be realized without the use of any complicated additional means in comparison with the now broadly available stutter box crimping appliances.

These and further objects, features and advantages of the present invention will become more clear when read in conjunction with the following detailed description of the invention to be set forth by reference to the several drawings, as well as the several examples. The drawings are provided only for illustrative purposes and only in a schematic manner.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional view of a preferred plant adapted for carrying out the present invention.

FIG. 2 is a schematic comparative and perspective view, illustrative of the generation of primary crimps according to the present invention in comparison with the known technique.

FIG. 3 is a schematic sectional view of part of FIG. 1, wherein, however, the upper nip roll has been omitted to more clearly represent the mode of generation of vertical crimps.

FIGS. 4 and 5 are enlarged cross-sectional views, illustrative of two and three layers of oriented and controlled fiber filaments when seen at the nip line, respectively.

FIG. 6 is a view similar to FIGS. 4 and 5, illustrative of a conventional comparative technique.

FIG. 7 is an enlarged top plan view of a batch of partially crimped filaments processed according to the known technique, wherein, however, the background has been drawn in black for sharp contrast of the illustrated features.

FIG. 8 is a view similar to FIG. 7, illustrative of the effects obtainable by the inventive process.

FIG. 9 is a side view of two groups of crimped filaments as discharged from a stuffer box, which have been treated separately, wherein however, the background has been shown in black for the same sharp contrasting purpose as set forth above.

FIG. 10 is a manual reproduction of a microphotograph showing several processed filaments according to the comparative conventional technique.

FIG. 11 is a view similar to FIG. 10, illustrative of crimped filaments processed according to the present inventive process.

FIG. 12 is a manual reproduction of an enlarged microphotograph illustrative of the known crimped filaments.

FIG. 13 is a view similar to FIG. 12, illustrative of processed filaments according to the novel teaching.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Now referring to the accompanying drawings, especially FIGS. -13, numerals 10 and 11 represent a pair of nip or feed rolls which are driven continuously in the respective directions shown by the arrows.

Before entering the nip line 0-0 (see FIG. 2) formed between the nip rolls 10 and 11, the synthetic filaments, generally shown at 12, may be substantially oriented parallel to and separated from each other by passing through a comb 18 and then introduced into a pre-heater 13 shaped into a hollow box through which steam, hot air, or a like heating medium is circulated in order to heat the filaments to a certain elevated temperature.

The orientation of the filaments prior to entering the nip line by passing them through a comb or reed is an optional step, the necessity for which depending upon the condition of the synthetic filaments 12 being fed to the nip line. In addition, the pre-heating step (i.e., passing the synthetic filaments 12 through preheater 13) is also optional, and may or may not be required depending upon the temperature of the synthetic filaments 12 fed to the nip line and depending upon the number of crimps desired in the filaments and the temperature to which at least one of the nip rolls is heated. The temperature to which the synthetic filaments are pre-heated depends upon the materials of which the filaments are composed. Although the pre-heating temperature varies between different synthetic resin filaments, generally the temperature of pre-heating will vary from 60 to or C. Specifically, when the filaments are composed of nylon, they may be pre-heated to a tempertature of from about 60 to 70 (2.; when they are composed of polyester material, they may be pre-heated to a temperature of from about 70 to 80 0; however, the maximum temperature employed is not at all critical and therefore one may sometlmes employ temperatures higher than the values just described. One skilled in the art can determine appropriate temperatures depending upon the results desired.

Passing the filaments through a comb or reed prior to entering the nip line aids in placing the filaments in a form parallel to each other making it easier to separate the crimped filaments after passing through the stufiing box. However, this step is optional, in that the comb or reed serves only as an auxiliary means for arranging the multifilament yarns equally spaced and parallel to each other.

Numeral 14 denotes a conventional stutfer box, opening towards the nip line formed between the rolls -11 so as to receive the filaments delivered by these rolls. The rear or outlet end of the stutfer box 14 is closed by a hinged cover which is loaded by a weight 17 which may be replaced by an adjustable spring, not shown.

According to the present invention, the filaments are mechanically and thermally controlled in their processing conditions as more specifically set forth hereinafter.

Assuming that the length of each of the nip rolls 10 and 11 is a predetermined value, the number of the filaments 12 is specifically selected so as to confine them into two or three compacted layers with the filaments being subjected to a considerable alteration of their cross-sectional configuration. This modified configuration may preferably be substantially pentagonal or hexagonal, as is most clearly seen from FIG. 4. In a three layer system of filaments as shown in FIG. 5, the intermediate series of filaments undergoes a lesser degree of deformation in the above sense. In order to attain this effect, the end extremities of the rolls 10 and 11 are covered by respective side covers, as is conventional so as to establish a positively confining, laterally-extending slit gap space, including the nip line above referred to.

The number of filaments to be fed to the nip line formed by the nip rolls (the nip line usually having a length of from about 40 to 100 mm.) varies and depends on the length of the nip and the denier and number of cfilaments constituting the yarn being fed to the nip line, as an example, when the nip line is 40 mm. long and the yarn is nylon, 840 denier/56 filaments, the number of yarns to be processed must be 30-50.

As a result of the formation of the 2 to 3 compacted layers and the lateral confining of the filaments at the nip line, the individual filaments at the nip line undergo some deformation of their cross-sectional configuration as is shown in FIGS. 4 and 5. This is necessary in order to assure that each of the individual filaments at the nip line intimately contacts each adjacent filament and thereby substantially fill the space existing at the nip line as can be seen by reference to FIGS. 4 and 5. By providing this configuration of filaments at the nip line, it is possible to obtain a uniform parallel vertical crimp in the filaments, the crimp being formed predominantly in the vertical direction perpendicular to the plane formed by the nip line.

The second requisite control condition for attaining the inventive results is to keep the filaments 12 within a predetermined elevated temperature condition, as will be more specifically described hereinafter. For this purpose, at least one of the nip rolls 10 and 11 may be provided therein with a suitable electrical resistance element, not shown, electrically connected with a heat current source. In addition to, or in the absence of, the electrical resistance element above mentioned, steam jet or jets, or warm water sprinklers may be provided for the same purpose.

In other words, regardless of the means used, at least one of the nip rolls should be heated. The manner in which at least one of the nip rolls is heated is immaterial, as long as the temperature to which at least one of the nip rolls is heated satisfies the following requirement. Generally, the temperature to which at least one of the nip rolls is heated thereby subjecting the filaments at the nip line to such temperature, varies up to a maximum of about 100 C. less than the fusing point of the synthetic resin constituting the filaments. Depending upon the particular synthetic resin, the temperature may vary but,

as a general guideline, the temperature is selected so as to invite a certain degree of plasticization of the synthetic resins constituting the filaments. The lower range of the temperature to which one of the nip rolls is heated is not critical, and may vary as desired, depending upon the particular synthetic resin constituting the filaments, the number of crimps desired in the filaments, the temperature of pre-heating if conducted, the pressure exerted between the nip rolls, etc. In other words, as long as the temperature does not exceed about 100 C. less than the fusing point of the synthetic resin constituting the filament, one of ordinary skill in the art can, by appropriate trial and error procedures, arrive at an appropriate lower temperature. As a general guideline, when dealing with nylon filaments, the temperature may vary from about to C. and when dealing with polyester filaments, the temperature may vary from 100 to C.

As seen from FIGS. 4 and 5, there are no substantial plays or free spaces in the lateral as well as vertical direction among the constituent filaments which feature can be well observed when comparing these figures with FIG. 6 which illustrates a conventional comparative process. In other words, according to the present invention the filaments are fed to the nip line such that they substantially fill the space formed thereby.

In FIG. 2, the 0-0 represents the nip line extending longitudinally, relative to the nip rolls 10 and 11 and therebetween the nip line being included in a lateral and horizontal plane A, assuming that the crimper plane is of the horizontal conventional type. The vertical plane denoted B is naturally perpendicular to said first plane A.,

In the present process, each of the filaments is provided with primary crimps in the vertical plane B, the number of these imaginary planes corresponding naturally to that of the filaments under processing. 0n the contrary, crimps are predominantly developed in the lateral plane A when a conventional technique is employed.

By the terminology primary crimps is meant that substantially all of the crimps produced in the filaments by the process by the present invention are in the vertical direction denoted by the vertical plane B. In other words, the number of crimps in the vertical direction perpendicular to the plane of the nip line is substantially 100% of the total number of crimps produced in the filament process of the present invention.

On the contrary, the lateral crimps (in plane A" of FIG. 2) formed in synthetic resin filaments using a conventional crimping process normally comprise substantially all of the crimps produced in such filaments by such a process, the filaments having little, if any, crimping in the vertical direction. It will be seen by the discussion contained hereinbelow that by feeding the filments to the nip line in a manner such as is indicated in FIG. 6 or in a number of layers greater than or less than from 2 to 3 compacted layers as presently required results in continuous filament yarns having an insufiicient number of crimps which is substantially lower than the number of crimps produced in the same fibers by the process of the present invention or in continuous filaments not having substantially all of the crimps in the vertical direction or being looped in configuration. In other words, the configuration of the filaments at the nip line and the heating of the filaments at the nip line to the indicated temperature are critical to the obtention of continuous filament yarns having a high number of crimps and substantially all of the crimps being of a looped character and being in a plane perpendicular to the plane formed by the nip line.

Conventional artificial crimps generated in the filaments by a known technique can be seen in FIGS. 10 and 12. Each of the crimps has a zigzag shape having straight line portions extending a substantial length and representing a sharp angular shape having a very minute apex. FIGS. 10 and 12 are manual reproductions from microphotographs taken at magnifying factors of X and 20X, respectively.

In FIGS. 11 and 13, corresponding to FIGS. 10 and 12, respectively, are illustrated several crimped filaments as processed according to the present invention. In these cases, the sharp angle formation has disappeared and the configuration of each of the generated crimps represents a loop, having a considerably large curvature. Intermediate straight line portions are substantially lacking. The processed filament has in effect a series of looped crimps which are substantially similar to those of the natural crimps formed on animal fibers and shows a remarkable difference from the prior art filaments shown in FIGS. 10 and 12.

The possibility of forming looped crimps as shown in FIGS. 11 and 13, relying only upon the stuffer box crimping technique, when combined with the present invention represents remarkable progress in the art.

As above stated, the number of monofilament layers fed to the nip line and the temperature to which the filaments are heated represent critical conditions in the process of the present invention. Further, although not critical, the pressure or force exerted by the nip rolls against the filaments passing through the nip line is important, since by varying the pressure, given a certain number of layers of filaments and a certain temperature, the number of crimps and the characteristics thereof can be varied depending upon the desired results. Generally, as an example, when the length of the nip line formed by the nip rolls varies from about 40 to 100 mm. in length, the force exerted by the nip rolls on the filaments passing through the nip line may vary from about 100 to 300 kgs.

When all of these conditions are satisfied, the continuous filaments fed through the nip line under such conditions undergo crimping to form primary crimps having the looped-shaped described above and illustrated in FIGS. 11 and 13. In FIGS. 1 and 2, these crimps are shown in an exaggerated fashion for illustrative purposes in order to more clearly understand the present invention. In addition, by referring to FIG. 3, it is noted that the looped crimps 19 generated by the present process are present in the form of straight lines within the stutfer box in view of the fact that the filaments are fed to the nip line and into the stuffer box in a uniform and straight fashion. It should be noted that FIG. 3 is merely illustrative.

When the filaments are oriented and controlled in the aforementioned manner and as shown in FIGS. 4 and 5, the whole filament assembly in the shape of 2 or 3 compacted layers is uniformly subjected to a vertical crimp ing action at the nip line which is the crux of the present process. Thus, the characteristics of the crimps may be easily modified merely by controlling the crimp-developing conditions at the place of the nip line.

The filament arrangement as shown in FIGS. 4 and 5 is in a compacted and stabilized condition and any tendency to produce lateral crimps is positively prevented.

If the number of layers of filaments at the nip line is increased to 4, the filaments constituting the intermediate two layers are not deformed to a suflicient extent to assure that only substantially vertical loops or crimps will be generated in the filaments. In other words, the effect of the present invention cannot be realized in view of the fact that the intermediate two layers of filaments are not subjected uniformly to a substanially vertical crimp as are the filaments constituting the outermost layers.

0n the contrary, when the number of layers of filaments at the nip line is reduced to much less than 2, spacing between the individual filaments will occur resulting in unfavorable conditions at the nip line such that substantially only vertical looped crimps cannot be produced in the filaments, rather, zig-zag type crimps 8 (i.e., of sawtooth configuration) are predominantly formed in the filaments when only a single layer thereof is fed to the nip line. Accordingly, a single layer arrangement of filaments at the nip line should be avoided. Example 1 given below describes a series of experiments that were carried out to show the criticality of the manner of feeding the filaments to the nip line in the process of the present invention. Example 1 also shows the effect of omitting heating at least one of the nip rolls.

As for the degree of thermal conditioning of the filaments at the place of the nip line, the degree of heating is selected such that not only the surfaces of the filaments are softened for the necessary modification of the crosssectional area of each of the filaments, but also the viscosity of the filament material is thereby increased so as to increase the adhesion between the filaments to such a degree that two or three mat-like, yet easily laterdivisible layers of filaments are provided.

The temperature to which at least one of the nip rolls is heated necessarily depends upon the particular material constituting the filaments. As a general guideline, the temperature should be sufficient to soften the filaments such that they can assume the configuration shown in FIGS. 4 and 5, but is less than that temperature which would result in fusing the individual filaments together thereby rendering separation after crimping virtually impossible. This is one of the primary aspects of the present invention, in that the filament layers are subjected to substantially uniform vertical looped crimping but the individual filaments or groups of filaments are easily separable after crimping.

The present invention will be more fully described by reference to the following examples, which are intended to be merely illustrative, and not limiting, in nature.

EXAMPLE 1 A multi-filament nylon 6, consisting of 56 filaments having an overall denier of 840 wherein each filament has a circular cross-section (i.e., diameter) of 0.0431 mm. and 14 twists per meter (in the Z-direction) was fed to the nip line formed between two nip rolls in varying numbers as shown in Table 1 given below. The length of the nip line formed by and between the nip rolls was 40 mm. The back pressure of the stuffing box on the other side of the nip rolls was adjusted to 1.25 kgs. per cm. (as measured on the surface of stutfer plate 15 contacting the filaments as seen in FIG. 1). The pressure (or force) exerted by the nip rolls on the filaments passing therebetween was adjusted to 40 'kgS. per cm. of nip line length; thereby equalling kgs. of total force.

Pre-heating means such as apparatus designated by the numeral 13 in FIG. 1 was utilized in several of the runs in this example, the pre-heating technique comprising spraying steam upon the filaments passing through the chamber. The nip rolls were also designed to be heated to a designated temperature. Where the filaments were fed to the nip line without heating the nip rolls, the pre-heating wasalso cut off such that the fibers were fed to the nip line cold (i.e., room temperature). Where the following Table indicates that the nip rolls were heated, the temperature of the nylon filaments fed to the nip line was raised to 60 C. by the pre-heating operation. I

After passing the filaments through the nip line, which was heated in certain circumstances and thus subjected to pre-heating in certain circumstances, the theoretical number of layers was calculated and also measured, and the appearance of the layers at the nip line was also determined. -For each set of filaments fed through such a stuffing box apparatus, the number and type of crimps were measured. The results are shown in the following Table 1.'

TABLE 1 Tempera- No. of ture multifil- No. of layers ament nip Crimps No. 01' Run bun- Rolls, Sum 1 Calcu- Meascrimps No. dles 0 (mm.) 1 lated ured Appearance of layers Direction Type per inch 1 16 5 Cold 39 1 1 sizazirliag be6t)ween filaments Lateral (cf. Fig. 7). Saw-tooth (cf. Fig. 12)

c 1g. 16 95 39 1 1 do- -do- 51 34 5 Cold 83 2 2 .-d0 -do do 22 34 95 83 2 2 Tig ihtly compacted (cf. Fig. Vertical (cf. Fig. 8)-. Looped 54 5 50 5 Cold 122 3 3 sp a lgirig begveen filaments Lateral Saw-tooth c ig. 6 50 95 122 3 3 'li5 h tly compacted (cf. Fig. Vertical (cf. Fig. 8).- Looped 58 7 66 5 Gold 161 4 4 Sp(acfing between filaments Lateral Saw-tooth 24 c 1g. 8 66 95 161 4 4 Substantially tightly comdo Mixture of looped and 60 pacted. saw-tooth.

N} TIotal 0! diameter of fils or linear length of filaments arranged at the 1p me 1 Calculated as follows: 0.0431 (diameter of individual filament) X56 (N o. of filament in bnndle)) (No. 0t bundles).

The results of this example as given in the above table can be interpreted as follows. With only a single layer at the nip line (Run Nos. 1 and 2), regardless of whether at least one of the nip rolls is heated, saw-tooth type crimps are developed in the filaments due to the spacing between individual filaments at the nip line as shown in FIG. 6. In spite of the fact that the number of crimps per inch in Run No. 2 was relatively high, the crimps were developed in a lateral direction and were of the saw-tooth configuration.

Run NOS. 3-6 show the number of filament layers at the nip line varying from 2 to 3, Run Nos. 3 and 5 exhibiting spacing between the individual filaments of the type in FIG. 6 and Runs 4 and 6 having the filaments tightly compacted as shown in FIGS. 4 and 5. Whereas the results of Runs 3 and 5 produced lateral saw-tooth crimps (the number of crimps being relatively low), Run Nos. 4 and 6 resulted in a large number of vertical looped crimps per inch. In addition, in Run Nos. 4 and 6, the individual filaments could be easily separated following crimping in comparison to Run Nos. 3 and 5. These results clearly show that heating at least one of the nip rolls is absolutely necessary to obtain a large number of vertical looped crimps and to assure that the filaments assume the proper form at the nip line.

By increasing the number of layers of filaments at the nip line to 4 (Run Nos. 7 and 8), and not heating at least one of the nip rolls (Run No. 7). spacing between the filaments at the nip line occurred and lateral saw-tooth crimps resulted (a relatively low number of crimps, in addition). Under the same conditions, and heating at least one of the nip rolls, the filaments were substantially tightly compacted at the nip line but lateral, rather than vertical, crimps resulted. In addition, the crimps were a mixture of looped and saw-tooth configurations, and although a high number of crimps per inch resulted, the configuration and direction of the crimps were not satisfactory.

The above results clearly show the criticality of the manner in Which the filaments are fed to the nip line and the conditions existing at the nip line.

EXAMPLE 2 A pair of nip rolls of the same type as employed in Example 1 was employed. The nip line measured 40 mm. by 1 mm. 100- multi-filaments of nylon 6, each filament bundle having an overall denier of 210 and being composed of 24 filaments, were oriented in parallel lines (by passing through a reed) and fed through the nip line into stutter box type crimper equipment, having a pivotable cover mounted at the delivery end of said box and loaded by a weight mass, thus producing a back pressure of 1-3 Cglczlated by dividing the total linear length of filaments at nip ne y 4 According to I IS 1074-1965, Standard Method 5.11.1. 5 Co1d=Room temperature (i.e., about 20 0.).

kgs./cm. Prior to feeding the filaments to the nip line, they were preheated to 60 C.

For the first experiment, the nip rolls were heated to C. and the nip roll pressure was adjusted to 1 kg./ cm. gage, when observed at the pneumatic cylinder provided for the pressure roll. The total roll force (at the nip line) was kgs. The filaments at the place of nip line were in the form schematically shown in FIG. 4.

In the second experiment, similar to the conventional comparative crimping technique, the nip rolls were kept in a cold state (i.e., room temperature) and the penumatic nip roll pressure was increased to double the initial value. The filaments, at the nip line, were in the form schematically shown in FIG. 6.

By the above-mentioned comparative tests, the following results were obtained.

TAB LE 2 Back pressure, kg./cm. of-

First experiment Second experiment 1 Elongation relative to the number of crimps (elongation/no. of crimps) 1s a measure of the crimp mode. In the second experiment, in view of the higher values, a longer wave-length is shown, thus representing sawtooth-like crimps.

As is seen from the foregoing, the use of heated nip rolls is highly elfective for the generation of lopped crimps.

As ascertained by further experiment, knitted fabrics made of yarns produced according to this invention (first experiment) provided considerably expandable knitted fabrics in comparison with those knitted from the yarns crimped by the second experiment. In addition, the knitted fabrics made of yarns produced according to this invention had a highly neat and beutiful appearance.

In the above experiments, the total diameters of the filaments fed to the nip line amounted to: 0.0329X24 100=79 mm., calculated as indicated in Table 1. The practical width (per layer) amounted to: 79/ 2=39.5 mm. which is substantially equal to the effective nip length of 40 mm. Thus, it can be seen that the filaments substantially completely filled the space of the nip line. Under the circumstances, the effective area of the filament layers maybe increased to -130% of the area of the nip line.

EXAMPLE 3 (Comparative) Using the apparatus described in Example 1 wherein the nip line had a length of 40 mm., 30 multi-filament bundles of nylon 6 yarns, each bundle having a total denier of 840 and being constituted of 56 filaments, were fed to the nip line. Preheating of the filaments was omitted and the nip rolls were cold; i.e., at room temperatureabout 20 C. The total force exerted by the nip rolls on the filaments was 200 kgs. The back pressure in the stufiing box was adjusted to 2 kgs. per cm.'-*.

The crimped yarns obtained had crimps predominantly in a lateral direction of the zig-zag or saw-tooth configuration, schematically represented in FIG. 12. The filament layers at the nip line were generally arranged into two layers, but spacing between the individual filaments occurred as is schematically represented in FIG. 6. Frequent lickings occurred in the crimped tow thus obtained, and it was extremely difficult to separate the tow into the con stituent filaments or small bundles thereof, since the filaments were entangled with one another.

EXAMPLE 4 The crimping apparatus was similar to that employed above. 40 and 15 nylon 6 multi-filament bundles, each having a total denier of 840 composed of 56 filaments, were oriented in parallel relationship and fed in separate experiments to the nip line. The filaments were preheated, in both cases, to 60 C. and the nip rolls were kept at 90 C. Nip pressure, as measured at the pneumatic cylinder was 1 kg./cm. gage, and the back pressure at the delivery end of the stuffer box was 2 kgs./cm.

In the first experiment using 40 multi-filament bundles, the filament batch was delivered at the nip line into the stutter box, in substantially three tightly overlapped layers as shown schematically in FIG. 5. Looped crimps were generated. The surface appearance of the processed batch was similar to that shown in FIG. 8. The larger wavy undulations are secondary crimps which are also of the vertical type. The side appearance was similar to that shown in FIG. 9. The extreme right-hand part of the crimped zone represents primary crimps and the larger undulations represent secondary crimps.

The total of the diameters of the processed batch (at the nip line) amounted to: 0.0431X56X40=96.5 mm. The effective nip line length was 40 mm. In practice, the filament batch represented substantially a three-layer sectional view, as shown schematically in FIG. 5. Actually, the number of total layers at the nip line was somewhere between 2 and 3.

In the second experiment, using 15 multi-filament bundles there was observed considerable spacing among the filaments at the nip line and overlapped layers, and thus considerable lateral crimps were developed.

The filaments may be fed to the nip line in such a manner that a different number of layers of filaments may exist at different portions along the nip line. As an example, a certain percentage of the filaments fed to the nip line may be in the form of two layers such as is schematically shown in FIG. 4 while the remaining filaments may be in the form of three layers as is schematically shown in FIG. 5. The only requirement is that the filaments be fed to the nip line in such a form and in such numbers as to assure that the filaments substantially fill the space existing at the nip line and form from two to three tightly compacted layers having slightly altered cross-sectional configurations as is discussed above and as is schematically shown in FIGS. 4 and 5.

Although the invention has been described above with reference to preferred embodiments, it is to be expressly understood that various changes and modifications may be made without departing from the spirit and scope of the present invention as defined by the appended claims.

What is claimed is:

1. In a process for crimping synthetic thermoplastic resin continuous filament yarns by forcibly passing said yarns against pressure into a stuffing box through a pair 12 of nip rolls, the improvement comprising producing vertical parallel looped crimps in said filament yarns in a direction substantially perpendicular to the plane formed by the nip line by:

arranging the filaments into from 2 to 3 compacted monofilament layers at the position where said layers enter the nip line by laterally confining the filaments at the nip line and supplying a sufiicient number of filaments such that the cross-section of said filaments are deformed at the nip line thereby assuring that each filament tightly contacts each adjacent filament and the filaments substantially fill the space existing at the nip line formed between said nip rolls; and feeding the thus arranged filaments into said stuffing box through said nip rolls at least one of which is heated to a temperature not exceeding 100 C. lower than the fusing point of the synthetic thermoplastic material constituting said continuous yarns.

2. The process of claim 1 wherein said continuous filament yarns are preheated prior to being fed through the nip line formed between said nip rolls.

3. The process of claim 1 wherein the force exerted between said nip rolls varies from about 100 to 300 kgs. as the length of the nip line formed between said nip rolls varies from 40 to 100 mm.

4. The process of claim 1 wherein a sufficient number of continuous filament yarns are fed to said nip line to insure that the total area of the filaments at the nip line is substantially equal to from about 2 to 3 times the area of the nip line formed between said nip rolls.

5. The process of claim 1 wherein a sufficient number of continuous filament yarns are fed to said nip line to provide substantially two compacted monofilament layers of filaments at the nip line wherein each filament in said two monofilament layers has a cross-sectional configuration of substantially pentagonal shape and is tightly contacted with each adjacent filament in the same monofilament layer and with the adjacent filaments in the other monofilament layer.

6. The process of claim *1 wherein a sufficient number of continuous filament yarns is fed to said nip line to insure that substantially three monofilament layers are formed at the nip line, the uppermost and lowermost monofilament layers comprising filaments Whose crosssectional configuration is substantially pentagonal, wherein the filaments constituting the intermediate monofilament layer have a substantially circular cross-sectional configuration, each of the filaments in each monofilament layer being in intimate contact with each adjacent filament in each monofilament layer and each adjacent filament in the adjacent monofilament layer.

7. The process of claim 1 further comprising separating the individual filaments from the resulting crimped tow.

8. The process of claim 1 wherein said synthetic thermoplastic material constituting said yarns comprises nylon or polyester.

9. The process of claim 1 wherein said continuous filament yarns are comprised of a polyester resin and wherein the temperature to which at least one of said nip rolls is heated varies from 100 to 110 C.

10. The process of claim 1 wherein said continuous filament yarns are comprised of nylon and wherein said temperature to at least one of said nip rolls is heated varies from to C.

11. The process of claim 10 wherein said continuous filament yarns are preheated to a temperature of from 60 to 90 C. prior to being fed to the nip line formed between said rolls.

(References on following page) 13 14 References Cited 3,065,519 11/1962 Starkie 2872 UNITED STATES PATENTS 3,340,585 9/1967 Buckley 281 ROBERT F. WHITE, Primary Examiner 3,316,612 5/1967 Stump 2872 6 R. R. KUCIA, Assistant Examiner 3,378,900 4/1968 Spicer 2872.14 CL 2,917,784 12/1959 Spence 264-168X 264-168 

